排尘孔涡轮冷却叶片叶顶流动与传热研究

涡轮叶片叶顶排尘孔用于清除冷气中掺杂的尘粒,以保证气膜孔和冲击孔的可靠工作,但排尘孔射流引起叶顶流动和传热问题。采用参数化方法建立有、无排尘孔涡轮冷却叶片几何模型,基于包含叶片主体、主燃气通道和三腔回流式内冷却通道的全局模型,采用流热耦合数值分析,开展排尘孔对涡轮冷却叶片叶顶流动与传热问题的初步研究。研究结果表明,对比有、无排尘孔叶片,排尘孔射流可降低叶顶平均温度约25 K;冷却通道对流换热作用和叶顶排尘孔射流可使叶顶平面降温400～600 K,冷却效果与冷却通道冷气流量和尘孔结构在叶顶位置相关;排尘孔叶顶射流对叶顶间隙高温燃气泄漏具有阻碍作用,可以提高叶片总压恢复系数约0.5%～1.5%,随着冷气流量的增大,这种作用增强;尘孔结构设计应兼顾射流对叶顶流动与传热的共同影响。

Tip Flow and Heat Transfer Prediction of Cooling Blade with Dirt Purge Holes

Dirty purge holes in the blade tip are used to extract dirt from the coolant flow through centrifugal forces such that these dirt particles do not block small diameter film-cooling holes and injection holes,to ensure safety and reliability of the blade.Whereas,the holes will affect blade tip flow and heat transfer.A numerical study of a turbine blade with dirt purge holes is performed to examine both flow and heat transfer characteristics.Two blade geometry models with and without dirty purge holes are established by a parametric method in CAD software.Coupled aerodynamic and heat transfer numerical simulation is used to predict the blade tip flow and heat transfer,with the integral of the blade solid field,main gas and internal cooling passage flow field.The result shows that,the cool air jet from purge holes can reduce the tip facet average temperature about 25 K,based on the contrast between blades with and without dirty purge holes.Convective heat transfer of internal cooling passage and jet flow of dirty purge holes can reduce the temperature of blade tips 400～600 K.The cooling effect relates to the position of dirt purge holes and the mass flow rate of cooling air.Furthermore,injection of dirt purge holes also reduces blade tip leakage,obviously.It will enhance the total pressure recovery efficient about 0.5%～1.5%,and the effect will be enhanced with the cooling mass flow rate increasing.So the flow and heat transfer influence of jet flow from dirty purge holes can’t to be ignored during the cooling turbine blade design.